1H NMR (400 MHz, CDCl3) δ 10.39 (s, 1H), 9.26 (d, J = 8.7 Hz, 1H), 7.94 (d, J = 7.3 Hz, 1H), 7.75 (s, 1H), 7.53 (t, J = 7.5 Hz, 2H), 7.39 (d, J = 8.0 Hz, 2H), 7.35 (d, J = 8.0 Hz, 2H), 2.49 (s, 3H), 2.46 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 193.41, 146.88, 137.80, 137.08, 136.69, 135.42, 132.31, 130.91, 130.33, 129.64, 129.23, 129.11, 126.13, 125.74, 124.82, 21.82, 21.28.